Various electronic devices, such as semiconductor devices, and photonic devices, such as lasers and solar devices, may include or may desirably include germanium-tin (GeSn) layers, such as GeSn, GeSnSi, GeSnSiC, and the like. For example, GeSn layers can be used to form direct bandgap devices and/or may be used as a stressor to provide strain in an adjacent germanium layer to increase mobility in the germanium layer. Similarly, GeSnSi and/or GeSnSiC layers can be used to form tunable band gap devices as well as optical devices having tunable optical properties.
In many applications, it may be desirable to include relatively large amounts of Sn in GeSn films to increase the strain in the film. The increased strain can lead to, for example, better electron and/or hole mobility in devices including such films.
It may also be desirable to provide GeSn films with relatively high levels of a p-type dopant (e.g., boron) to form GeSn films having relatively low contact resistance. Generally, the higher the concentration of p-type dopant in the film, the lower the contact resistance.
Unfortunately, during p-type doped GeSn film formation, the p-type dopant and the Sn can compete with each other for inclusion in the film. As a result, as an amount of p-type dopant in the film increases, an amount of Sn that can be included in the film decreases. Similarly, as an amount of Sn in the film increases, an amount of p-type dopant that can be included in the film decreases.
Accordingly, improved methods of and systems for forming GeSn films that can allow relatively high levels of Sn and/or p-type dopant in the films are desired. Additionally, GeSn films having relatively high concentrations of p-type dopant and/or Sn, and structures and devices including such films, are desired.